Combustion furnace



0, 1954 A. B. CARGILL COMBUSTION FURNACE Filed July 12, 1952 H.F. GEN.

INVENTOR Alexander B.Corgi|l.

Patented Aug. 10, 1954 COMBUSTION FURNACE Alexander B. Cargill, Dunkirk, N.

Y., assignor to Allegheny Ludlum Steel Corporation, Brackenridge, Pa., a corporation of Pennsylvania Application July 12, 1952, Serial No. 298,647

Claims. 1

This invention relates to combustion furnaces and in particular to the combustion tubes employed therein.

In accordance with prior art practice combustion furnaces have been utilized for efiecting cornbustion of metallic components for use in conjunction with analyzer and the like, for testing the composition of the metallic components, In such prior art devices the combustion tubes of the furnaces have been formed of relatively expensive material, such as quartz and the like, and considerable expense has been incurred in operating such furnaces by reason of the breakage of such combustion tubes.

In a well known combustion furnace presently sold to the trade, the combustion tube formed of quartz is provided with an elongated end portion through which a quartz tube extends to direct the flow of oxygen to the metallic component which is to be combusted. In practice the end of such tube is about A; inch from the metallic components with the result that as combustion occurs, the impingement of the stream of oxygen on he metallic components causes spatte-ring of the molten metallic component with the result that the oxygen tube often becomes plugged thus reducing the flow and, in some cases, completely stopping the flow of oxygen into the combustion chamber. In addition, the spatter ng often causes displacement of the oxygen tube with the result that the stream of oxygen is not directed toward the metallic component which is to be combusted thereby resulting in an incomplete or inefficient combustion of such component. Further it is found that the spattering of the molten metallic components on the quartz causes strains in the glass to the degree that the glass tubes are frequently broken during the combustion of the metallic component with the result that the test is ruined. This also greatly adds to the cost of testing such metallic components, it being found in actual practice that the known combustion tube has an average life of only '75 tests with a maximum of not over 200.

An object of this invention is to provide, in a combustion furnace for an analyzer, for the emcient combustion of a metallic component which is to be tested.

Another object of this invention is to provide a combustion tube of ceramic material for a combustion furnace, the combustion tube having a main body portion forming the combustion chamber and an elongated end portion integral therewith and having an orifice for directing a centered stream of oxygen into the combustion chamber into contact with a metallic component which is to be tested, the combustion chamber cooperating with the orifice and the metallic component to permit expansion of the stream of oxygen to reduce the force thereof and thereby prevent spattering of the metallic component as it is combusted while at the same time providing an adequate oxygen supply to maintain an emcient combustion.

Other objects of this invention will become apparent when taken in conjunction with the accompanying drawings in which:

Fig. 1 is a view in sectional elevation of a combustion furnace embodying the teachings of this invention, and

Fig. 2 is a view partly in elevation and partly in section of the combustion tube of the furnace as taken along the line 22 of Fig. 1.

Referring to the drawing, Fig. 1 of this invention is illustrated by reference to a combustion furnace Ii) formed of a base portion l2 and an upper combustion tube M mounted as by means of plate flanges E6 and E8 on the end wall 20 of a housing (not shown) for a high frequency generator and other test equipment. The combustion tube ii is preferably of a ceramic material such as porcelain, mullite or zircon or the like. An induction coil 22 is permanently carried by the end wall 20 for receiving the combustion tube 14, the terminals of the induction coil 22 extending in an insulated manner through the end wall to the high frequency generator (not shown).

As illustrated in Figs. 1 and 2, the combustion tube [4 comprises a lower main portion 24 forming a combustion chamber 26 and an elongated upper end portion 28 having a passageway 30 therethrough terminating in an orifice 32 at the upper end of the combustion chamber 26. The main body portion 2t and the elongated end portion 28 are formed as an integral ceramic tube, each of the portions having the same longitudinal axis. The combustion chamber 28 has a substantially constant cross sectional area of a diameter considerably larger than that of the passageway so of the upper end portion 28. As illustrated, the orifice 32 is disposed in substantially the plane of junction of the end portion of the main body portion 24 so that the orifice 32 opens directly into the substantially constant cross sectional area of the combustion chamber 26, the purpose of which will be explained more fully hereinafter.

As representative of the practical dimensions of an eflicient combustion furnace, reference may be had to a furnace in which the combustion chamber 26 has an inside diameter of about 1 inches with the passageway 30 having an inside diameter of about inch. Such a combustion tube is provided with an overall length of about 9% inches with the combustion chamber having an overall length of from 5% to 5% inches. While the side walls forming the main body portion 24 may be relatively thin, that is of a thickness of about 7 inch, it is preferred that the side walls of the upper end portion 23 have a thickness somewhat greater than the side walls of the main body portion 2Q in order to withstand clamping strains and physical shock when clamped into position as will be described hereinafter. In practice a dimension of inch is found to be practical for thickness of the side walls of the upper end portion 28.

In assembling the combustion tube 14 on the end wall 20, the combustion tube it is provided with an adaptor 34 which may be of aluminum or the like and is disposed to closely fit about the outside portion of the elongated portion 28. The adaptor 34 is of a size to fit within an opening in the flanged plate Hi, the edge of the opening of the plate l8 and the edge of the adaptor 3% being of stepped design as illustrated at 36 so that when the adaptor is fitted within the opening of the flanged plate iii, the adaptor 3 1 will be tightly held in such assembled position and the combustion tube i l having the adaptor 35 disposed about the elongated end portion 28 thereof will be positioned centrally of the induction coil 22 with the lower end of the combustion tube M projecting through an opening 38 in the lower plate flange member It.

As illustrated, the opening 38 of the plate flange i6 is also provided with an annular adaptor 40 of aluminum or the like which is frictionally held in position within the opening 38, the lower edge of the annular adaptor it being bevelled as at 32 for receiving a ring i l of rubber which is fitted in sealing engagement with and about the lower end of the combustion tube It when the tube Hi is assembled as described. The ring 44 thus functions to aid in positioning the combustion tube It as well as for effecting a seal between the combustion tube 14 and the bevelled surface 42 of the adaptor 40.

In order to hold the combustion tube It in the assembled position as just described, a spring clamp member it carried by the end wall 26 of the housing (not shown) is provided with spring fingers 48 and 58 disposed to clamp about the outer surface of the upper elongated end portion 28 adjacent the adaptor 34 to thereby prevent vertical movement of the combustion tube It. A flexible tubing 52 of rubber or the like is disposed to connect the open end of the elongated end portion 28 with a suitable source (not shown) of oxygen to provide a supply of oxygen for the combustion furnace. The passageway 38 of the elongated ceramic end portion 28 thus functions as an oxygen tube for delivering oxygen directly into the substantially constant cross sectional area of the combustion chamber 26.

The lower base portion I2 is formed of an annular member 54 carried on the upper end of a rod member 56 which is disposed for vertical movement in response to a manual operation of an operating handle 58. In order to guide the movement of the lower base portion l2, a bracket se is carried on the end wall 28, the rod 56 being disposed for vertical movement through the bracket 6d. The annular member 5A is provided with a substantially fiat upper surface 62 having an upwardly extending annular flange 64 about its outer periphery which fiange is also provided with a bevelled inner surface 86 disposed to fit against and in sealin engagement with the rubber ring is carried by the lower end of the combustion tube it. As illustrated the upper end of the rod 56 and the lower portion of the annular portion 54 are drilled as at 68 and iii, respectively, to form interconnecting passages, the passage it being provided with a flexible conduit 12 of rubber or the like for providing an outlet for the products of combustion from the furnace when the base member is seated with the bevelled edge 56 seated against the rubber ring as as described.

In order to support a crucible is within the confines of the induction coi1 22, a ceramic pedestal i6 is disposed to seat on the annular member 54 carried by the rod 56 as illustrated. The

ceramic pedestal it has its lower end slotted or V drilled to form passages 18 therethrough so that the products of combustion flowing downwardly between the pedestal l6 and the inner surface of the wall of the combustion tube 14 can pass therethrough to the interconnecting passages 58 and ill to the gaseous outlet '52. A metallic plug is fitted within the ceramic cylindrical pedestal iii so as to prevent entrapment of gases internally of the pedestal and to insure the flow of the gases as described. The crucible it, of course, contains the metallic component 82 which is to be combusted and analyzed.

In Fig. l the operating handle 58 is illustrated as being locked in position to maintain the base portion E2 in sealed relation with the upper combustion tube It, this locked relation being effected by reason of the operating handle 53 being positioned on a lug 84, carried by a bracket 85 which is secured to the end wall 20. As illustrated a pivotally mounted strap 88 is disposed on the lug 812, for movement between pins 90 and 92, pin 92 being so positioned that as the strap 88 abuts the pin 92 and the handle 58 is seated on the lug 84, the strap 38 is slightly oif center and the free end thereof projects into the horizontal path of movement of the handle 58 to prevent horizontal movement of the handle 58 away from its seat on the lug 84.

When it is desired to lower the crucible M from the combustion chamber 26, the strap 38 is moved to a position where it abuts the pin 90 and the free end of the strap 88 is out of the horizontal path or movement of the handle 53 whereby the operating handle 58 can then be manually moved from its seated position with respect to the lug 34 to permit the rod 55 to slide downwardly in its bracket 68. In practice, the bracket St is disposed a suflicient distance from the plate flange l6 so that when the base portion 12 is lowered by movement of the operating handle 58 as described, the annular member 54 will seat against the bracket 66 and the crucible 74 will be free from the confines of the lower body portion 2d of the combustion tube is. It is thus seen that a crucible can be efiiciently loaded with a metallic component which is to be tested, placed in position on the pedestal l6 and then by manual movement of the operating handle 58 the base portion can be so raised that the crucible Hi is moved to a position within the combustion chamber 26 where the crucible ill will be within the confines of the induction coil 22. At the same time an efiicient and effective seal is obtained by reason of the presence of the rubber ring 44 about the end of the induction tube l4, seated against the bevelled edges 42 and' lit-of the adaptor land the annular portion 54 of the base member.

In practicing this inventionit is preferred thatthe crucible be positioned within the confines of the induction coil 22 so that the crucible way 30 having a diameter of about 1% inch whenthe induction coil 14 is energized to effect an efficient combustion of the metallic component 82. It is thought that such an efficient combustion without accompanying spattering of the components is effected by havin the orifice open directly into the substantially constant cross sectional area of-the combustion chamber 26. Thus as the stream of oxygen flows from the passageway 38 through the orifice 32 it is directed in a centered. stream onto the metallic component 82 and the relatively large cross sectional area of the combustion chamber 26 permits an expansion of the stream of oxygen as it flows from the orilice to the crucible M to reduce the force of such stream and thereby prevent spattering. At the same time, the cross sectional area of'the chamber 26 is suiiiciently large to provide an adequate supply of oxygen above'the crucible M to maintain and support efiicient combustion of the metallic component 82 contained in the crucible it. The flow of oxygen sweeps the gaseous products of combustion downwardly between the side walls of the pedestal l6 and the combustion chamber 25 through the passageways I3, 68 and 1%] to the gaseous outlet '12 from whence they are conducted to any suitable gaseous analyzer (not shown), the details of which form no part of this invention and therefore'will not be described.

In practice, a very efficient operation of the combustion furnace utilizing the combustion tube I4 as described is obtained, it being found that very accurate analyses are obtained by effecting the combustion in the apparatus described. Further, it is found that by eliminating the spattering of the metallic component which is to be tested, the passageway 30 is not plugged at the orifice 32 and the oxygen is directed at all times into the crucible 74. Further, the reduction of spattering prevents breakage of the combustion tube l l with a resultant improvement in the life of the combustion tube of as high as 2400 tests. In addition to a greatly prolonged life of the combustion tube it is also found that sinc the combustion tube is formed of a ceramic, the initial cost of the tube is greatly reduced from that of the quartz tube formerly used.

What is claimed is:

1. In a combustion furnace for use with an analyzer for testing a metallic component, the furnace being disposed to be supplied from a source of oxygen and provided with a crucible for holding the metallic component, the crucible being carried by a base member disposed for movement to position the crucible within the confines of an induction coil, the combination comprising, a combustion tube of ceramic material having a main body portion and an elongated end portion at one end thereof, the elongated end portion being of smaller diameter than the main body portion, the elongated end portion having a passageway longitudinally therethrough of about inch diameter terminating in a fixed orifice open to the main body portion, the other end of the passageway being disposed to be supplied from the source of oxygen whereby'the oxygen flows through the passageway in direct contact with the ceramic material of the clon gated end. portion, the other end of the mainbody portion being open, the combustion tube" being disposed with its main body portion positioned lengthwise within the induction coil-and about the positioned crucible with the fixed'orifice spaced about 1% inches from the crucible,-v

the space between the fixed orifice and the crucible being open to permit the direct flow of city-- gen from the orifice to the crucible, the Openend of the combustion tube being disposed to receive the base member in seating engagement therewith to close said open end of the tube when the base member is moved to position the crucible within the confines of the inductioncoil, the passageway cooperating in the combustion tube in directing a constantly centered stream of oxy'-' gen directly against the metallic component in the positioned crucible.

being carried by a base member disposed for movement to centrally position the crucible within the confin s of an induction coil, the combination comprising, a combustion tube of ceramic material having a main body portion and an elongated end portion at one end thereof with both portions having the same longitudinal axis,

the elongated end portion being of smaller diameter than the main body portion, the elongated end portion having a passageway longitudinally therethrough, said passageway being of about inch diameter and terminatingin afixed centrally located orifice at one end of and open to the main body portion, the other end of the passageway being disposed to be supplied from the source of oxygen whereby the oxygeniiows through the passageway in direct contactwith the ceramic material of the elongated end portion, the other end of the main body portionbeing open, the combustion tube being disposed with its main body portion positioned lengthwise within the induction coil and about the centrally positioned crucible with the passageway in direct alignment with the crucible and the fixed orifice spaced about 1% inches from the crucible, the: space between the fixed orifice and the crucible being open to permit the direct flow of oxygen from the orifice to the crucible, the open end'ofthe combustion tube being disposed to receivethe base member in seating engagement therewith to close said open end or the tube when the base member is moved to centrally position the cru-' cible within the confines or the induction coil,- the passageway cooperatin in the combustiontube in directing a constantly centered stream of oxygen directly against the metallic component in the centrally positioned crucible.

3. In a combustion furnace disposed to be supplied from a source of oxygen for use withan 7 tudinally therethrough, said passageway being of about M inch diameter and terminating in a fixed centrally located Orifice at the one end of and open to the main body portion, the other end of the passageway being disposed to be supplied from the source of oxygen whereby the oxygen fiows through the passageway in direct contact with the ceramic material of the elongated end portion, the other end of the main body portion being open, the combustion tube being disposed with its main body portion positioned lengthwise within the induction coil and about the centrally positioned crucible with the passageway in direct alignment with the crucible and the fixed orifice spaced about 1%; inches from the crucible, the space between the fixed orifice and the crucible being open to permit the direct flow of oxygen from the orifice to the crucible, the open end of the combustion tube being disposed to receive the base member in seating engagement therewith to close said open end of the tube when the base member is moved to centrally position the crucible within the confines of the induction coil, the orifice of the passageway cooperating to efiectively discharge the oxygen in a substantially centered stream directly to the metallic component, the main body portion cooperating with the spaced orifice and crucible to eifect an expansion of the stream as it flows from the orifice to the crucible to efieotively reduce the force thereof as the oxygen contacts the metallic component to prevent spattering thereof during combustion while maintaining sufficient oxygen adjacent the metallic component to eiiect an efficient combustion thereof.

4. In a combustion furnace disposed to be supplied from a source of oxygen for use with an analyzer for testing a metallic component disposed in a crucible carried by a base member which is disposed for movement to position the crucible within the confines of an induction coil, the combination comprising, a combustion tube of ceramic material having a main body portion and an elongated end portion at one end thereof disposed about the same longitudinal axis, the main body portion having a combustion chamber of substantially constant cross-sectional area throughout its length, the elongated end portion having a substantially smaller cross-sectional area than that of the main body portion, the elongated end portion having a passageway disposed longitudinally therethrough terminating in a fixed centrally located orifice open to the substantially constant cross-sectional area of the combustion chamber, the other end of the passageway being disposed to be supplied from the source of oxygen whereby oxygen flows through the passageway in direct contact with the ceramic end portion, the other end of the main body portion being open to receive the crucible, the combustion tube being disposed with its main body portion positioned lengthwise within the induction coil and the passageway in direct alignment with the crucible, the orifice being in spaced relation to the crucible to maintain them about 1 /4 inches apart when the crucible is positioned within the combustion chamber within the confines of the induction coil, the space between the orifice and the crucible being open to permit the direct flow of oxygen from the orifice to the crucible, the orifice of the passageway cooperating to efiectively discharge the oxygen in a substantially centered stream directly to the metallic component, the substantially constant cross-sectional area of the combustion chamber cooperating with the 8 spaced orifice and crucible to efieot an expansion of the stream of oxygen as it fiows from the orifice to the crucible to eifectively reduce the force thereof as the oxygen contacts the metallic component to prevent spattering thereof during combustion while maintaining sufficient oxygen adjacent the metallic component to efiect an efficient combustion thereof.

5. In a combustion furnace disposed to be supplied from a source of oxygen for use with an analyzer for testing a metallic component disposed in a crucible seated on a pedestal centrally disposed on a base member which is disposed for movement to position the crucible within the con fines of an induction coil, the combination comprising, a combustion tube of ceramic material having a main body portion and an elongated end portion at one end thereof disposed about the same longitudinal axis, the main body portion having a combustion chamber of substantially constant cross-sectional area throughout its length, the elongated end portion having a substantially smaller cross-sectional area than that of the main body portion, the elongated end portion having a passageway disposed longitudinally therethrough terminating in a fixed centrally located orifice open to the substantially constant cross-sectional area of the combustion chamber, the other end of the passageway being disposed to be supplied from the source of oxygen whereby oxygen flows through the passageway in direct contact with the ceramic end portion, the other end of the main body portion being open to receive the crucible, the combustion tube being disposed with its main body portion positioned lengthwise within the induction coil and the passageway in direct alignment with the crucible, the open end of the combustion chamber being disposed to receive the base member in seating engagement therewith to close said open end of the combustion chamber, the pedestal disposed on the base member having a length sufficient when the base member is in seating engagement with the combustion tube to centrally position the crucible seated thereon in the combustion chamber within the confines of the induction coil, the orifice and positioned crucible being spaced apart about 1 inches, the space between the fixed orifice and the crucible being open whereby the oxygen fiow through the passageway is delivered in a substantially centered stream directly to the metallic component in the crucible, the substantially constant cross-sectional area of the combustion chamber cooperating with the spaced orifice and crucible to effect an expansion of the stream of oxygen as it flows from the orifice to the crucible to effectively reduce the force thereof as the oxygen contacts the metallic component to prevent spattering thereof during combustion while maintaining sufiicient oxygen adjacent the metallic component to effect the efficient combustion thereof.

Dreher Nov. 14, 1944 

